The present invention concerns incandescent light bulbs and more particularly deals with the problem of extending the life-time of incandescent light bulbs.
Incandescent light bulbs used for street lighting have to be replaced as soon as possible after having "burnt out". This is within the responsibility of town or city organisations who have to rely on a maintenance staff kept for that and for like purposes.
Even more difficult becomes the situation in those cases where incandescent light bulbs are used in apartment buildings in which public areas, such as, courtyards, staircases and like places are lighted by means of such bulbs. Here, the responsibility for replacing burnt out light bulbs is frequently shared by many, the result being that replacement is not effected as quickly as required.
As is well known, the life-time of an incandescent bulb is governed by the quality of the glowing wire and by the voltage under which the lamp operates.
Reducing the voltage fed to a light bulb may result in prolonging the effective life-time of the latter. It is known to reduce the voltage by means of resistances, transformers or dimming devices. These, however, are quite expensive to install and themselves have a limited life-time. Moreover, devices of this kind are consumers of energy which is practically lost.